Method and apparatus for removing moisture, air, and dirt from lubricating oil

ABSTRACT

A method and an arrangement in a circulation lubrication including a lubricating oil tank, pressure pipe lines for supplying oil to parts to be lubricated, and return pipe lines for returning the oil from the parts to be lubricated to the oil tank. To remove air and dirt from the oil, the flow returning from the parts to be lubricated to the lubricant tank is divided into at least two superimposed flow portions, using a plate member, so that the oil flow portion containing air bubbles forms the upper flow portion and the flow portion containing water and heavy particles forms the lower flow portion.

BACKGROUND ON THE INVENTION

The invention relates to a method which is suitable for implementationin a circulation lubrication system comprising a lubricating oil tank;pressure pipe lines for supplying oil to parts to be lubricated; returnpipe lines for returning the oil from the parts to be lubricated to theoil tank; means for pumping oil into the pressure pipe lines; andadjusting means for maintaining a desired lubrication situation, whereinthe flow returning from the parts to be lubricated to the lubricant tankis divided into at least two superimposed flow portions so that the oilflow portion containing air bubbles forms the upper flow portion and theflow portion containing water and heavy particles forms the lower flowportion. The invention further relates to structure provided in acirculation lubrication system.

Circulation lubrication systems are today used widely to lubricatevarious machines especially when the lubricant is used for cooling thepart needing lubrication. An example of the use of circulationlubrication is the lubrication of the bearings of the drying cylindersin paper machines or the lubrication of gas turbines. In both cases thebearings are subject to a thermal load from the outside.

Circulation lubrication is also used when the part to be lubricatedcreates considerable dissipation power. One example of such applicationsis the lubrication of gear boxes.

Still another use of circulation lubrication is in cases where thelubricant may get dirty in the part to be lubricated, and it should bepossible to reuse the lubricant after cleaning.

A circulation lubrication system usually comprises a pump operated by anelectric motor. The pump brings the oil into motion. The output of thepump is usually selected so that it exceeds the required flow rate by 10to 20%, so that a sufficient operating margin is left for the control ofbypass pressure. Oil is arranged to pass through replaceable filters.The filters are often arranged in two groups so that one group can beseparated by means of valves and the filters changed without having tostop the entire assembly. An electric or steam-operated heater is oftenused for further heating the oil. The oil is cooled by a heat exchangerhaving water or air cooling means. The cooling power is adjusted by atemperate regulator provided for supply oil. The set value of thetemperature regulator is often typically about 55° C. Pressure controlis often effected by a bypass valve back to the oil tank. Depending onthe system, the set values of the pressure controller typically varybetween 5 and 20 bar.

Oil is supplied to parts needing lubrication, such as different parts ina paper machine, by means of pressure trunk pipes usually made of arustproof material. The oil flows in the pipes as a laminar flow, so thepressure drop is small. From the trunk pipes the oil is distributed to aplurality of flow metering boards wherefrom it is divided into risingpipes to be supplied to a number of parts to be lubricated. From theseparts the oil is passed through return pipes by utilizing gravitationinto collector pipes on the return side. The oil is passed under theinfluence of gravitation through the collector pipes into the tank ofthe circulation lubrication assembly. The pipes on the return side arenever full of oil. The inclination of the pipes is about 2 to 3% towardsthe tank of the assembly. Before the tank, the return oil is passedthrough a coarse-mesh filter. Oil returned into the tank is then againsucked into circulation by the pump. The dimensions of the tank areusually such that the oil stays in the tank for 10 to 50 minutes,depending on the viscosity of the oil.

In the system the tank has several functions for conditioning the oilbefore recirculation. One function of the tank is to allow air (betterdescribed as gas) bubbles contained in the oil to rise to the surface.Air bubbles may increase the liability of the pump to cavitation, andthey may deteriorate the lubricant film formed on the part needinglubrication. Another function is to allow large dirt particles having adensity considerably higher than that of oil to deposit on the bottom ofthe tank. To some extent water better described as aqueous condensatedrops contained in the oil will also fall down in the tank. The densityof water is so close to that of oil that the falling speed is low. Thetank condenses moist air flowing in the return pipes on the tank wallsand drains the water along the walls, thus collecting the water on thebottom of the tank. The tank also cools the oil through the walls.Furthermore, the tank forms a space into which the pipe lines areemptied at system shutdowns, and the tank serves as an oil storagevessel in the case of a pipe leakage, so that the machine to belubricated can be shut down controllably. Still another function of thetank is to ensure that there is always oil in the pump suction means inorder that air will not be sucked along. The moisture and suitabletemperature also enable bacteria to grow in the tank.

The tank has also associated thermostat-controlled oil heaters, whichmay be electric heaters or steam-operated heaters. The heaters are usedto heat the great amount of oil contained in the oil tank within 4 to 8hours typically to about 55° C., before the system is started as thescrew pumps used are not able to pump cold oil of high viscosity at fullpower without the risk of cavitation.

In principle, the systems described above operate well; in practice,however, they have several drawbacks as a result of which the operationof the systems is not the best possible. One drawback is the entrainmentof moisture, air and heavy dirt particles through the return pipes tothe tank, as air in the form of air bubbles is carried along with theoil, and water is formed as a result of condensation, for example. Dirtparticles are mixed with the oil e.g. at the parts to be lubricated.These drawbacks are especially apparent in paper machines as thereplenty of both dirt and moisture below the hood in the drying section.Moreover, it is to be noted that the temperature is high below the hooddue to the steam heating of the drying cylinders. The moisture contentof air is high due to the moisture evaporated from the paper web. Forthis reason, a large amount of water is condensed in the oil, whichcauses problems in the tank, as the moisture, air bubbles and dirt haveto be removed from the oil before the oil is again fed from the tank tothe parts to be lubricated.

SUMMARY OF THE INVENTION

The object of the invention is to provide a method and an arrangement,by means of which the drawbacks of the prior art can be eliminated. Thisis achieved by means of a method according to the invention, which ischaracterized in that the upper flow portion is passed close to thesurface of the oil contained in the tank, and that the lower flowportion is passed close to the bottom of the tank. The arrangementaccording to the invention, in turn, is characterized in that the platemember is arranged to pass the upper flow portion close to the surfaceof the oil contained in the tank and the lower flow portion togetherwith a substantially parallel control plate close to the bottom of thetank.

An advantage of the invention is mainly that the moisture, air and dirtcan be removed very efficiently from the oil returning from the parts tobe lubricated. Another advantage of the invention is that it is simple,so that its reliability in operation is high and it is economical totake into use. The invention also allows the operation of thecirculation lubrication system to be improved as the quality of oil canbe kept higher than previously. This is due to the fact that theinvention enables the oil to be cleaned very efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail withreference to the preferred embodiments shown in the attached drawings,wherein

FIG. 1 is a general view of a circulation lubrication system for a papermachine;

FIG. 2 is a fragmentary longitudinal vertical sectional view of a firstembodiment of the arrangement according to the invention;

FIGS. 3 and 4 are sectional views taken in different directions of asecond embodiment of the arrangement according to the invention;

FIG. 5 is a sectional view of an oil tank in which an assembly formed bythe units shown in FIG. 3 and 4 is placed;

FIG. 6 is a general view of a preferred oil tank arrangement in thearrangement according to the invention; and

FIG. 7 is a general view of another preferred oil tank arrangement inthe arrangement according to the invention.

DETAILED DESCRIPTION

FIG. 1 is a general view of a circulation lubrication system for a papermachine. The reference numeral 1 indicates an oil tank, and thereference numeral 2 indicates generally an assembly comprising pumps,filters and other similar devices. The reference numeral 3 showspressure pipe lines for supplying oil used as a lubricant to parts 4 tobe lubricated, in this special case drying cylinders in the papermachine. Further in FIG. 1, the reference numeral 5 indicates returnpipe lines for returning the oil from the parts to be lubricated to theoil tank 1. The structure and operation of the system shown in FIG. 1are obvious to one skilled in the art, so these matters will not bedescribed more closely herein.

The invention is specifically concerned with the return oil side of thecirculation lubrication system. FIG. 2 is a general view of a firstembodiment of the arrangement according to the invention. The samereference numerals as in FIG. 1 are used in FIG. 2 for correspondingparts. According to the essential idea of the invention the flowreturning from the parts 4 to be lubricated to the lubricant tank 1 isdivided into at least two superimposed flow portions A, B so that theflow portion containing air bubbles forms the upper flow portion A, andthe flow portion containing water and heavy particles forms the lowerportion B. The flow is divided by means of at least one plate member 6.The division of the flow into two portions takes place so that the upperflow portion A passes along the plate member 6 into the tank 1. Thelower flow portion B passes into the tank along the bottom part of thepipe 5 and a control plate 7 forming an extension of the pipe. Inaddition, a perforated plate 8 is provided in order to make the floweven as the speed of the flow upon the plate member 6 and that of theflow upon the control plate may be unequal. The flow portion B is passedby means of the plate member 6 and the control plate 7 close to thebottom of the tank 1. The flow portion A, in turn, remains close to theupper surface of the oil contained in the tank so that the air bubblesare able to rise quickly to the surface.

The plate member 6 and the control plate interest the oil surface at anangle such that the formation of air bubbles is insignificant when theoil flow interests the oil surface. The intersection angle may vary from0 to 60 degrees. In the prior art, it has been a common practice thatthe oil drops freely from the pipe on the oil surface, so that verylarge amounts of foam have been formed. Large dirt particles arecollected e.g. by means of a grate 9. The grate 9 is obvious to oneskilled in the art.

FIGS. 3 to 5 show a second preferred embodiment of the arrangementaccording to the invention. This embodiment comprises a plurality ofplate members 6 positioned one upon another with a mutual spacing suchthat they divide the oil flow into several superimposed flow portions.The idea is realized by a honey-combed unit 10 shown in FIG. 5. It isassembled of parts 10a shown in FIGS. 3 and 4. The honey-combed unit 10may be positioned in the oil tank 1 as shown in FIG. 5. Oil is arrangedto flow through the unit so that the plate member 6 in each part 10a ofthe unit divides the flow into two portions as shown in FIG. 3, so thatair, water and heavy dirt particles are separated from the flow.

Being lighter than oil, air rises upward while water and heavy dirtparticles, being heavier than oil, fall downward. In this way the airbubbles are collected on the lower surface of the plate member 6, wherefrom they pass upward into a discharge pipe 11 due to their lightnessand the inclination of the plate member 6. Correspondingly, water anddirt particles are collected on the upper surface of the plate member 6,along which they pass under the influence of their weight into a pipe 12to be discharged.

The parts 10a are piled one upon another so that a flow path is providedfor oil between two adjacent parts 10a, i.e. the plate members 6 in theparts 10a divide the flow into superimposed portions, as describedabove. A grate structure 13, 14 is positioned above and below each platemember 6. The grate structure is arranged to guide air bubbles and dirtparticles entered between the individual walls 13a, 14a of the gratestructure in a substantially vertical direction. Spacings between theparts 10a are so small that the vertical distance of travel required forair, water and dirt is short and the separation takes place over a shortoil flow distance. In practice, the walls 13a, 14a of the gratestructure catch the air bubbles and dirt entered between them. Betweenthe walls 13a, 14a, the dirt particles and air bubbles pass vertically,as mentioned above. The dirt particles pass downward to the uppersurface of the plate member 6 of the next lower part 10a, while the airbubbles pass on to the lower surface of the next upper plate member 6,etc. The flow is made even by means of a plate 15. The plate is ofconventional structure. Spaces 16, 17 in the tank are for collectingwater. The pump of the circulation lubrication system sucks oil from aspace 18. The reference numeral 19 indicates a thermal insulation whichensures that the temperature of oil exceeds 45° C. throughout the oilcontained in the tank. It is to be noted that if the temperature of oildrops to e.g. 30° C. and there is moisture present in the tank, optimalgrowing conditions for bacteria will be created, and air begins to beformed in the tank. Bacterial growth is inhibited, e.g., by keeping thetemperature within the range from 45° to 60° C.

FIG. 6 shows an example of a lubricating oil tank 1 suitable for thearrangement according to the invention. The tank 1 may comprise e.g. twotank modules 1a, which is an advantageous solution in that it sparesspace.

FIG. 7 is a general view of a second preferred embodiment of thearrangement according to the invention. An advantage of this embodimentis that the tank is very small. Oil returning from the parts to belubricated enters the tank 1 through the pipe 5. A floating surfaceflow-levelling means 20 follows the surface of the oil when the surfacelevel varies. The float parts keep the levelling means 20 on thesurface, and the laths 25 allow the air bubbles entered between them torise upward. The device is secured to the inner wall of the tank, e.g.,by means of a wire rope.

Each plate member 6 comprises a grate plate and a plate portion. Thegrate plates separate the plate portions from the oil flow. Between thegrate plate and the plate portion, the flow of air and water is oppositein direction to the main flow of oil. Paths 21 allow air bubbles to riseupward, while paths 22 allow moisture to fall down on the bottom of thetank 1.

The embodiments described above are by no means intended to restrict theinvention, but the invention may be modified within the scope of theclaims as desired. Accordingly, it is evident that the arrangementaccording to the invention or its details need not necessarily be suchas shown in the figures but other solutions are possible as well. Forinstance, the oil tank may be of any shape, comprise various modules,etc.

I claim:
 1. A method implemented in a circulation lubrication systemwhich includes a lubricating oil tank having a bottom and containing oilhaving an upper surface, at least one pressure pipe line for supplyingthe oil from the tank to at least one part to be lubricated, at leastone return pipe line for returning the oil from said at least one partto said tank, at least one pump for pumping the oil from said tank intosaid at least one pressure pipe, and adjustment structure formaintaining a desired lubrication situation in said system for said atleast one part,said method comprising:(a) dividing said returning oilinto at least two vertically superimposed flow portions, including anupper flow portion containing gas bubbles, and a lower flow portioncontaining at least one of aqueous condensate and heavy particles; (b)passing said upper flow portion into said tank adjacent said uppersurface; and (c) passing said lower flow portion into said tank adjacentsaid bottom of said tank.
 2. The method of claim 1, further including:insteps (b) and (c) intersecting each said flow portion with said uppersurface at an angle ranging between 0° and 60° to said upper surface. 3.The method of claims 1, wherein:said at least two verticallysuperimposed flow portions comprise at least three verticallysuperimposed flow portions, each one additional to said upper and lowerflow portions being disposed between said upper and lower flow portions.4. A circulation lubrication system, comprising:at least one part to belubricated; a lubricating oil tank having a bottom and arranged tocontain oil having an upper surface; at least one pressure pipe line forsupplying the oil from said tank to said at least one part to belubricated; at least one return pipe line for returning the oil fromsaid at least one part to said tank; at least one pump for pumping theoil from said tank into said at least one pressure pipe; adjustmentstructure for maintaining a desired lubrication situation in said systemfor said at least one part; and at least two plate members interposed insaid at least one return pipe line and arranged for dividing saidreturning oil into at least two vertically superimposed flow portions,including an upper flow portion containing gas bubbles, and a lower flowportion containing at least one of aqueous condensate and heavyparticles, and forpassing said upper flow portion into said tankadjacent said upper surface; and passing said lower flow portion intosaid tank adjacent said bottom of said tank, each said plate memberbeing disposed for supporting a respective said flow portion, and saidplate members being substantially parallel to one another.
 5. Theapparatus of claims 4, wherein: said plate members are spatiallyarranged to cause said respective flow portions supported thereon tointersect said upper surface at an angle ranging between 0° and 60° tosaid upper surface.
 6. The apparatus of claims 4, wherein: said at leasttwo plate members include at least three plate members arranged tosupport at least three superimposed flow portions, each one additionalto said upper and lower flow portions being disposed between said upperand lower flow portions.
 7. The apparatus of claims 6, furthercomprising: an upper grate structure, and a lower grate structureassociated with each said plate member and respectively arranged to passsaid gas bubbles encountered thereby substantially vertically upwardlyand said heavy particles encountered thereby substantially verticallydownwardly.
 8. The apparatus of claims 7, wherein:each said plate memberslopes forwardly downward, has a lower surface arranged for guiding saidgas bubbles towards an upper end thereof for discharging upwardly, andan upper surface arranged for guiding said aqueous condensate and heavyparticles towards a lower end thereof for discharging downwardly.